In the field of factory automation (FA) for automating factory production processes, automatic control equipment using programmable logic controllers (PLCs) is used. In this FA field, an FA system is constructed by disposing PLCs in the FA system. Thus, when a large-scale FA system is constructed, a plurality of PLCs are connected by a network.
When PLC systems are connected using a network, network units for connection to the network are used. There are various kinds of network units that are compatible with communication protocols or network configurations. Thus, a user can select and use network units appropriate for an FA system to be constructed.
When a PLC system is constructed, a simulation is performed to check the operation of a PLC program executed by a PLC. In the simulation, a virtual PLC to simulate the operation of an actual PLC is constructed on a computer, and it is checked whether the operation of the virtual PLC is a desired one. This enables correction of problems in the PLC program without constructing a PLC system itself, thus allowing a reduction in the cost of constructing an FA system.
In a simulation method described in Patent Literature 1, one personal computer (PC) operates one virtual PLC, and operations between virtual PLCs on a network are simulated and verified, using a PC network.